Explain why is O=C=O nonpolar while R—O—R is polar.

O=C=O nonpolar because the dipole moment of the two C=O bonds are exactly equal and opposite of each other. Therefore, they cancel each other and so, the net dipole moment of O=C=O is zero. Whereas, the net dipole moment of R—O—R is not equal to zero because the shape of this compound is non-linear and thus, R—O—R is polar in nature.